BCL9 as a Key Player in Wnt/β-catenin Signaling: Implications for Osteogenesis, Tissue Repair, and Oncology

B-cell lymphoma 9 (BCL9) is a regulatory protein that plays a key role within the Wnt/β-catenin signaling pathway. In recent years, it has garnered significant attention across the domains of tissue repair and tumour biology. The Wnt/β-catenin signaling pathway is of great importance in regulating bone tissue formation and osteoblast differentiation. As a co-activator of β-catenin, BCL9 is capable of governing bone development and regeneration by augmenting the transcriptional activity of the Wnt signaling. In addition, BCL9 is also closely related to diverse biological processes, such as angiogenesis, muscle regeneration and tumour progression. Research findings have indicated potential correlations between BCL9 and the treatment of osteoporosis, fracture healing, as well as other bone-related ailments, thereby positioning it as a crucial target in the exploration of bone regeneration. In oncology research, BCL9 affects tumour cell proliferation and metastasis by regulating the Wnt/β-catenin pathway, thus emerging as a promising target for anticancer therapy. In this paper, we conducted a comprehensive review of the discovery, structure, and mechanism of action of BCL9 within the Wnt/β-catenin signaling pathway, along with its potential applications in bone development, tissue regeneration, and cancer therapy, with the intention of furnishing novel perspectives and a theoretical foundation for future investigations.